Adjustable straps are frequently used in sporting equipment, particularly footwear, to provide a releasable-yet-rugged attachment for securing a user's foot in the footwear—such as ski boots, snowboard boots, in-line skates, and the like—and/or for securing the footwear to a sports device, such as a snowboard or ski. A ubiquitous strap for such applications is the serrated strap, also commonly referred to as a “ladder strap.” A ladder strap is generally a flexible, elongate strap having a plurality of closely-spaced, transverse ridges or teeth that are adapted to engage a buckle assembly, typically a ratchet-type buckle, whereby the buckle releasably holds the strap in a tensioned condition.
The teeth of a ladder strap are generally integrally formed in the strap and typically have a triangularly-shaped profile, although other profile shapes, such as square or trapezoidal, are sometimes used. A buckle assembly commonly includes a movable holding element that is biased towards the teeth of a ladder strap inserted in the buckle. The buckle is adapted to permit the ladder strap to be inserted and pushed through the buckle in one direction for tightening, while inhibiting or preventing the strap from backsliding in the opposite direction. A lever or other device is provided on the buckle that allows the user to move the holding element away from the ladder strap, whereby the strap can be loosened. Many buckle assemblies further include a tightening apparatus—for example, a levered ratchet-type device—that drivably engages the ladder strap teeth. A ratchet-type buckle permits the user to apply relatively high tension in the strap for a tight fit. The teeth of the strap must be rugged enough to repeatedly endure the significant stresses that may be applied by the ratchet assembly to tighten the strap.
A typical application for a ladder strap is shown, for example, in FIG. 1, wherein a snowboard binding assembly 90 is mounted on a snowboard 93. The snowboard binding assembly 90 includes a buckle 100 that is attached to an instep pad 95. The instep pad 95 includes a strap that couples the buckle 100 to the medial side of a binding frame (not shown). The buckle 100 engages a ladder strap 80 having a plurality of sawtooth shaped, transverse teeth 85. The ladder strap 80 is coupled to the lateral side of the binding assembly 90. The binding assembly 90 is secured to the snowboard 93 and receives the snowboard boot between lateral and medial sides thereof. In this particular example, the ratchet-type buckle 100 includes a transversely-mounted, rotatable toothed barrel 140 that engages some of the strap teeth 85, and a lever 170 that provides leverage for driving the toothed barrel 140 to securely tighten the strap 80. It will be appreciated that very significant stresses can thereby be applied to the teeth 85 of the strap 80 by the toothed barrel 140.
In typical applications relating to sporting footwear, the ladder strap must be flexible enough to conform to the curved outer contours of the user's boot—for example, about the ankle, instep, or toe portion of the boot—while also being strong enough to be retained by a clasping mechanism during vigorous use. Flexibility is also required to permit the user to insert the strap into the fastener assembly, and to permit the strap to flex out of the user's way for easy insertion or removal of the user's foot in the binding (or into the boot itself in other applications such as skates, etc.). Moreover, because ladder straps are frequently used with alpine and other snow sports equipment and footwear, the ladder strap must exhibit the desired flexibility and strength at low temperatures and in wet environments.
In particular, in the examplary snowboarding binding application shown in FIG. 1, the ladder strap 80 must be soft and flexible at cold temperatures, so that the strap 80 can be easily fed into the ratchet buckle 100; and it must not break when bent at a sharp angle or stepped on. The strap teeth 85 must be strong enough that they are not sheered off or otherwise damaged by the high stresses imparted by the ratchet-buckle toothed barrel 140 during tightening of the strap, and during subsequent rigorous snowboarding.
It has always been a challenge in designing ladder straps to find or select one material that is strong enough to withstand the forces that will be applied to the teeth of the strap and yet produce a strap that is flexible enough to operate properly at cold temperatures without becoming brittle or cracking, and wherein the strap can be easily fed into the ratchet buckle. Moreover, it will be appreciated that a typical day of snowboard riding may require releasing and securing the binding strap numerous times—for example, to release the boot from its binding prior to ascending the mountain on a chair lift and then, upon arrival, re-securing the strap prior to riding down the trail.
The problems associated with prior art ladder straps are seen most clearly from the fact that, in practice, ladder straps are the most commonly replaced parts in the snowboard binding industry. They have the highest failure rate and require the greatest number of replacement parts ordered for warranty. Improving the performance and durability of the ladder strap could save manufacturing costs and reduce cost and inconvenience to the end user.